Such a kind of conventional bellows type mechanical seal, when taking an example of a stationary form, is provided with a seal ring which is held by a bellows, and a mating ring which is arranged in opposition to the seal ring in a manner as to slidably contact therewith, wherein it is constructed such that the seal ring is supported by a housing, and the mating ring is supported by a rotating shaft so as to rotate together with the rotating shaft (see a first patent document).
The bellows is an integral structure in which a retainer for holding the seal ring is welded and fixed to one end of the bellows and a collar fixedly secured to the housing is welded and fixed to the other end of the bellows.
The seal ring is made of a sliding material such as carbon, and is hermetically shrink fitted or press fitted to the retainer. As a retainer material, there is used a metallic material having a low thermal expansion coefficient of about 5×10−6 1/degrees C., which is approximate to the coefficient of thermal expansion of carbon, etc., such as, for example, 42% Ni—Fe, etc. By making the coefficient of thermal expansion of the seal ring approximate to that of the retainer, a change in the shrink fit margin can be reduced even if it becomes a high temperature, so that a change in shrink fit stress can be reduced, and the flatness of the end faces of the seal can be held.
On the other hand, for the bellows, there is used a metal having a spring nature, such as Inconel 718, Inconel 625 (Inconel is a registered trademark), AM350, etc.